Knee Cap Dislocation
Knee cap dislocation, also known as patella dislocation, occurs when the knee cap is completely displaced out of its normal position. The knee cap runs in a groove on the front of the femur, called the trochlea. When the knee cap is knocked out of this groove, a dislocated patella always goes to the outer (lateral) side of the knee. As a result, the muscles on the inner side of the knee are damaged and the ligaments can be torn or stretched.
Dr. David Colvin, orthopaedic surgeon in Perth. David's specialty is knee and shoulder surgery and sports injuries.
What causes Knee Cap Dislocation?
Patella dislocation is caused by a direct blow to the front of the knee or from a sudden pivoting of the leg, forcing the knee cap to the outside.
Some people are more at risk of patella dislocation. Risk factors include:
- Maltracking or tilt of the patella.
- Being generally loose jointed.
- Being knock kneed.
- Having a high knee cap.
- Being born with a shallow groove for the knee cap (shallow trochlea).
Patella maltracking is a very common problem. Even a normal knee cap has a tendency to run towards the outer half of the groove. In some people this can be quite severe, resulting in maltracking and patella tilt. Sometimes the patella does not completely dislocate. It may feel like it is partly slipping out, which is called patella subluxation.
What are the symptoms of Knee Cap Dislocation?
A knee cap dislocation is a very dramatic event which causes sudden severe pain and an inability to straighten the knee. Usually the knee cap is visible sitting in a very abnormal position on the outer half of the knee. If you straighten the knee, the patella may come back into its normal position with a sudden clunk.
A small number of people dislocate their patella and it comes back into position immediately. They may not even be aware that the knee cap was dislocated briefly.
It may be necessary to go to hospital to have the knee cap put back into place. Even once it’s back in place, the knee usually becomes very sore and swollen over the following days.
Some people experience patella subluxation where it partially dislocates and then comes back into position spontaneously. This can be very unnerving and the knee can feel like it’s going to give way.
Tibial Tubercle Transfer
Get in touch with us!
Dr David Colvin consults at:
Western Orthopaedic Clinic
Suite 213, 25 McCourt Street,
Subiaco WA 6008 (Perth)
- These rooms are part of St John of God Subiaco Hospital.
- Parking is available on site.
Dr David Colvin operates at: